I am working on a website with a digg/scribd like layout. Users can make their own accounts (optional). I want my users to be able to keep journals where they can upload pics and write posts, complete with tagging and user comments. I'm thinking something like a light version of Wordpress or similar CMS would be nice. Wordpress itself would be a huge overhead on the server if every user was running an instance of it. What's an efficient way to go about doing this?